An example of conveying device for conveying a thin platy work in a vacuum environment is disclosed in the Patent Document 1. The conveying device includes a pair of link arm mechanisms provided on a swivel base. An end portion of each of the link arm mechanisms is provided with a hand which is capable of horizontally holding a platy work such as a glass substrate for a liquid crystal display panel. When the swivel base rotates about a vertical axis on a fixation base, the pair of link arm mechanisms rotate correspondingly. When the link arm mechanisms swivel, the platy work held by the hands is moved linearly within a horizontal plane. Thus, the platy work is transported from a predetermined position to another position.
Another example of conveying device is disclosed in the Patent Document 2. The swivel base of the conveying device is provided with a guide rail for supporting and guiding the hand in a predetermined direction when the link arm mechanisms swivel. With this arrangement, the hand holding the platy work can be moved linearly in a more stable attitude.
Such conveying devices are used widely in e.g. a manufacturing process of liquid crystal display panels for moving platy works in and out of a process chamber. In such a manufacturing process, the conveying device is used for transporting heated glass substrates in a vacuum environment in a clean process, for example.
However, the above-described conventional conveying device may not endure the thermal environment in transportation of heated platy works in a vacuum environment. Specifically, in using the conveying devices, the fixation base is disposed in an atmospheric environment while the swivel base is disposed in the space inside of a transportation chamber kept in a vacuum condition, for example. In transportation of the platy work, when the heated work is held by the hand, radiation heat irradiated from the work may cause deformation of the link arm mechanisms close to the hand. Thus, it may become difficult to ensure transportation accuracy.
Further, in cases where the swivel base is disposed in a vacuum environment, a vacuum seal is provided at an appropriate position such as a periphery of the swivel base for ensuring the vacuum, for example. In transportation of heated platy works, the vacuum seal is subject to heat from the platy works. Thus, the function of the vacuum seal may be deteriorated, resulting in diminishing airtightness.
Patent Document 1: JP-A-2005-186259
Patent Document 2: JP-A-2005-125479